<template>
  <el-color-picker
    v-model="theme"
    :predefine="['#409EFF', '#1890ff', '#304156','#212121','#11a983', '#13c2c2', '#6959CD', '#f5222d', ]"
    class="theme-picker"
    popper-class="theme-picker-dropdown"
  />
</template>

<script>
const version = require("element-ui/package.json").version; // element-ui version from node_modules
const ORIGINAL_THEME = "#409EFF"; // default color
export default {
    data() {
        return {
        chalk: "", // content of theme-chalk css
        theme: ""
        };
    },
    computed: {
        defaultTheme() {
            return '#409EFF';
        }
    },
    watch: {
        defaultTheme: {
            handler: function(val, oldVal) {
                this.theme = val;
            },
            immediate: true
        },
        async theme(val) {
            const oldVal = this.chalk ? this.theme : ORIGINAL_THEME;
            if (typeof val !== "string") return;
            const themeCluster = this.getThemeCluster(val.replace("#", ""));
            const originalCluster = this.getThemeCluster(oldVal.replace("#", ""));
            // console.log(themeCluster, originalCluster);
            const $message = this.$message({
                message: "正在切换主题",
                customClass: "theme-message",
                type: "success",
                duration: 0,
                iconClass: "el-icon-loading"
            });
            const getHandler = (variable, id) => {
                return () => {
                const originalCluster = this.getThemeCluster(
                    ORIGINAL_THEME.replace("#", "")
                );
                const newStyle = this.updateStyle(
                    this[variable],
                    originalCluster,
                    themeCluster
                );
                let styleTag = document.getElementById(id);
                if (!styleTag) {
                    styleTag = document.createElement("style");
                    styleTag.setAttribute("id", id);
                    document.head.appendChild(styleTag);
                }
                styleTag.innerText = newStyle;
                };
            };
            if (!this.chalk) {
                const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`;
                await this.getCSSString(url, "chalk");
            }
            const chalkHandler = getHandler("chalk", "chalk-style");
            chalkHandler();
            const styles = [].slice
                .call(document.querySelectorAll("style"))
                .filter(style => {
                const text = style.innerText;
                return (
                    new RegExp(oldVal, "i").test(text) && !/Chalk Variables/.test(text)
                );
                });
            styles.forEach(style => {
                const { innerText } = style;
                if (typeof innerText !== "string") return;
                style.innerText = this.updateStyle(
                innerText,
                originalCluster,
                themeCluster
                );
            });
            this.$emit("theme-change", val);
            $message.close();
        }
    },
    mounted(){
        var color=localStorage.getItem('theme-color')
        if(color){
            this.theme=color
        }
    },
    methods: {
        updateStyle(style, oldCluster, newCluster) {
            let newStyle = style;
            oldCluster.forEach((color, index) => {
                newStyle = newStyle.replace(new RegExp(color, "ig"), newCluster[index]);
            });
            return newStyle;
        },
        getCSSString(url, variable) {
            return new Promise(resolve => {
                const xhr = new XMLHttpRequest();
                xhr.onreadystatechange = () => {
                if (xhr.readyState === 4 && xhr.status === 200) {
                    this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, "");
                    resolve();
                }
                };
                xhr.open("GET", url);
                xhr.send();
            });
        },
        getThemeCluster(theme) {
            const tintColor = (color, tint) => {
                let red = parseInt(color.slice(0, 2), 16);
                let green = parseInt(color.slice(2, 4), 16);
                let blue = parseInt(color.slice(4, 6), 16);
                if (tint === 0) {
                // when primary color is in its rgb space
                return [red, green, blue].join(",");
                } else {
                red += Math.round(tint * (255 - red));
                green += Math.round(tint * (255 - green));
                blue += Math.round(tint * (255 - blue));
                red = red.toString(16);
                green = green.toString(16);
                blue = blue.toString(16);
                return `#${red}${green}${blue}`;
                }
            };
            const shadeColor = (color, shade) => {
                let red = parseInt(color.slice(0, 2), 16);
                let green = parseInt(color.slice(2, 4), 16);
                let blue = parseInt(color.slice(4, 6), 16);
                red = Math.round((1 - shade) * red);
                green = Math.round((1 - shade) * green);
                blue = Math.round((1 - shade) * blue);
                red = red.toString(16);
                green = green.toString(16);
                blue = blue.toString(16);
                return `#${red}${green}${blue}`;
            };
            const clusters = [theme];
            for (let i = 0; i <= 9; i++) {
                clusters.push(tintColor(theme, Number((i / 10).toFixed(2))));
            }
            clusters.push(shadeColor(theme, 0.1));
            return clusters;
        }
    }
};
</script>

<style>
.theme-message,
.theme-picker-dropdown {
  z-index: 99999 !important;
}
.theme-picker .el-color-picker__trigger {
  height: 26px !important;
  width: 26px !important;
  padding: 2px;
}
.theme-picker-dropdown .el-color-dropdown__link-btn {
  display: none;
}
</style>